Liquid crystal panel substrate, liquid crystal panel, and electronic equipment and projection type display device both using the same

ABSTRACT

The present invention is a liquid crystal panel substrate that comprises: pixel units each having a pixel electrode, to be used as a reflective electrode and arranged in a matrix pattern on a substrate, and a switching element controlling a voltage applied to the pixel electrode; wherein between the pixel electrode and a conductive layer forming a terminal electrode of the switching element, a contact hole is provided for connecting the pixel electrode and the terminal electrode. A light-shielding layer, having an opening surrounding the portion in which the contact hole is formed, and having no opening in regions between a plurality of adjacent pixel electrodes, is formed between the pixel electrode and the conductive layer. Harmful effects due to light leaking through a space between the pixel electrodes can thereby be prevented.

This is a Division of application Ser. No. 10/682,537 filed Oct. 10,2003, which in turn is a Division of application Ser. No. 09/091,544filed Jul. 1, 1998, which is a National Stage of PCT/JP97/003802 filedOct. 21, 1997. The disclosures of the prior applications areincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to liquid crystal substrates andreflective-type liquid crystal panels using the substrate, and inparticular, relates to a technique that can preferably be applied toactive-matrix liquid crystal panels in which pixel electrodes areswitched by switching elements formed on the substrate. Furthermore, thepresent invention relates to electronic equipment and projection typedisplay devices both using the liquid crystal panel.

2. Background of Related Art

Conventionally, as active-matrix liquid crystal panels used for lightvalves of projection type display devices, liquid crystal panels havinga thin film transistor (TFT) array, employing amorphous silicon, on aglass substrate as switching elements of pixels have been put intopractical use.

Active-matrix liquid crystal panels using the above TFTs have low TFTelement mobility and a large device size. Thus, for example, aprojection type display device, such as a projector, equipped with theliquid crystal panel as a light valve, is disadvantageously large insize. Furthermore, transmissive-type liquid crystal panels have thefollowing fatal disadvantage: the aperture ratio decreases as theresolution of the panel increases, such as XGA or SXGA, since theregions of the TFTs provided for every pixel do not transmit light.

As compared with the transmissive-type active-matrix liquid crystalpanels, reflective-type active-matrix liquid crystal panels are small insize and have an insulated gate field effect transistor (MOSFET) arrayformed as switching elements on a semiconductor substrate so as tocontrol the voltage applied to pixel electrodes which are to be used asreflective electrodes.

As is mentioned above, in active-matrix liquid crystal panels havingtransistor elements formed on a glass or semiconductor substrate, whenlight leaks through spaces formed between the pixel electrodes,hole-electron pairs are generated in a PN junction (e.g., a junctionbetween source/drain regions and a channel region of the transistor, ora junction between source/drain regions and a well) of the semiconductorlayer or semiconductor substrate, so that a light leakage current flowsand undesirably destabilizes the electric potential of the semiconductorlayer, the semiconductor substrate, or the well. In the case ofreflective-type liquid crystal panels, the amount of light leakage canbe reduced as compared with that of the transmissive type by, forexample, forming the pixel electrodes close to each other in the toplayer without using particular light-shielding means. However, inreflective-type liquid crystal panels used for light valves ofprojection type display devices, strong light is converged and isincident on the spaces between the pixel electrodes. Thus, it is notsufficient to arrange the pixel electrodes close to each other to avoidthe light leakage current.

In particular, since liquid crystal panels with a semiconductorsubstrate have well regions, the leaking light transmitted through notonly the transistor portion but also the portion at a certain distancefrom the transistor portion may cause a light leakage current.Therefore, unless sufficient countermeasures are taken, the lightleakage current increases as compared with liquid crystal panels havingTFTs as switching elements on a glass substrate.

Furthermore, in active-matrix liquid crystal panels having transistorelements on a glass or semiconductor substrate, peripheral circuits suchas a scanning side driving circuit and a data line driving circuit areformed on the same substrate; there is a problem such that the lightleakage current is generated and the peripheral circuits are operated bymistake when light enters to such peripheral circuits.

Moreover, in reflective-type liquid crystal panels, an insulating filmis exposed by the spaces between the pixel electrodes, and the lightreflected by the surface of the insulating film changes its direction by180° and emerges. As a result, the emerging light is displayed asunwanted light, which deteriorates the quality of the image.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide atechnique by which the amount of light leaking through the spacesbetween pixel electrodes is reduced so that the light leakage currentgenerated in a substrate decreases.

Another object of the present invention is to provide a technique forreducing the amount of light leaking into the pixel region andperipheral circuits without increasing the number of the process stepsin reflective-type liquid crystal panels in which pixel electrodes arearranged in a matrix pattern and peripheral circuits are providedoutside the pixel region.

Still another object of the present invention is to provide a techniquefor preventing adverse effects on image quality due to the lightreflected by the surface of an insulating film exposed to the spacesbetween the pixel electrodes in reflective-type liquid crystal panels.

The first through eighteenth aspects of the invention are discussedbelow.

First, a liquid crystal panel substrate comprises: pixel units eachhaving a pixel electrode to be used as a reflective electrode andarranged according to a matrix pattern on a substrate; and a switchingelement controlling a voltage applied to the pixel electrode;

in which between the pixel electrode and a conductive layer comprising aterminal electrode of the switching element, a contact hole is made forconnecting the pixel electrode and the terminal electrode; and

a light-shielding layer, having an opening surrounding the portion inwhich the contact hole is formed, and having no opening in regionsbetween a plurality of adjacent pixel electrodes, is formed between thepixel electrode and the conductive layer. The amount of light leakingthrough the space between the pixel electrodes and reaching theswitching element can thereby be reduced to substantially zero.

Secondly, an anti-reflection film is provided between the pixelelectrode and the light-shielding layer. The light which is incident onthe space between the pixel electrodes and reflected by the surface ofthe light-shielding layer can thereby be absorbed even when thelight-shielding layer is formed of a metallic layer having a relativelyhigh reflectance, such as aluminum.

Thirdly, the anti-reflection film has substantially the same shape asthat of the pixel electrode and is provided below the pixel electrode.Thus, the following phenomenon can be prevented: the light, which isincident on the space between the pixel electrodes, is repeatedlyreflected between the surface of the light-shielding layer and the backsurface of the pixel electrodes, leaks through an opening provided atthe portion of a connecting conductor connecting a pixel electrode and aswitching electrode, reaches a semiconductor layer or a semiconductorsubstrate, and generates a light leakage current.

Fourthly, the anti-reflection film is made of titanium nitride. Titaniumnitride has excellent adhesion to the pixel electrode such as Al and hasexcellent light absorbance.

Fifthly, the film thickness of the titanium nitride is 500 to 1000angstroms. This range is preferable to absorb visible light.

Sixthly, in regions between a plurality of adjacent pixel electrodes, agroove at least having a slope is formed on the surface of an underlyinginsulating layer of the pixel electrode or on the surface of thelight-shielding layer under the underlying insulating layer. The lightentering through a space between the pixel electrodes can thereby bereflected in an oblique direction. Thus, the following phenomenon can beprevented: the light incident on the space is reflected by thelight-shielding layer, emerges through the space, and is mixed with thelight reflected by the pixel electrodes. As a result, the contrast ofthe liquid crystal panel can be improved.

Seventhly, the anti-reflection film has substantially the same shape asthat of the pixel electrode and is provided below the pixel electrode.The light reflected by the surface of the insulating film, exposed byspaces between the pixel electrodes, or the light-shielding layer belowthe insulating film, is thereby absorbed into the anti-reflection filmformed on the back surface of the pixel electrodes so that the light isprevented from emerging while changing its direction is changed by 180°,resulting in improved image quality.

Eighthly, the anti-reflection film is made of titanium nitride.

Ninethly, the film thickness of the titanium nitride is 500 to 1000angstroms. The effects thereof are similar to those of the fourth andfifth effects.

Tenthly, the contact hole is provided at a substantially centralposition of the plane of the pixel electrode. The distance between theend portion of the pixel electrode and the opening provided in thelight-shielding layer is therefore substantially the same for each endportion. Thus, the travel distance of the light, entering through aspace between the adjacent electrodes and reaching the contact hole, isincreased and the light cannot readily reach the switching element side.

Eleventhly, a liquid crystal panel substrate comprises pixel units whichare arranged in a matrix pattern on a substrate, and each of which has apixel electrode to be used as a reflective electrode and a switchingelement controlling a voltage applied to the pixel electrode;

wherein a pixel region comprising a plurality of the pixel units and aperipheral circuit provided at a peripheral region of the pixel regionare formed on the same substrate; and

a light-shielding layer comprising the same layer as the reflectiveelectrode of the pixel region is formed above the peripheral circuit.The amount of light leakage in the pixel region and the peripheralcircuit can thereby be reduced, without increasing the number of stepsfor producing the liquid crystal panel substrate.

Twelvethly, the light-shielding layer is positioned at a peripheralregion surrounding the entire periphery of the pixel region including aregion in which the peripheral circuit is not formed. The pixelelectrodes are positioned around the pixel region and serve as“partitions”.

Thirteenthly, in the pixel region, a second light-shielding layer isprovided between the pixel electrode and the switching element, and thesecond light-shielding layer is also provided in a region between thefirst light-shielding layer, which is provided above the peripheralcircuit, and the pixel electrodes that are outermost in the pixelregion. In the pixel region, the entrance of light from the borderbetween the pixel region and the peripheral circuit region can beprevented by providing the second light-shielding layer under the pixelelectrode.

Fourteenthly, between the pixel electrode and a conductive layercomprising a terminal electrode of the switching element, a contact holeis made for connecting the pixel electrode and the terminal electrode;

a second light-shielding layer, having an opening surrounding theportion in which the contact hole is formed in the pixel region andhaving no opening in regions between a plurality of adjacent pixelelectrodes, is formed between the pixel electrode and the conductivelayer; and

in the peripheral circuit, the second light-shielding layer is alsoprovided below the first light-shielding layer and is used as aconnecting line portion in the peripheral circuit. Thus, multi-layerwiring can be achieved in the peripheral circuit portion by utilizingthe light-shielding layer in the pixel region, and the driving circuitand the like can be integrated.

Fifteenthly, the second light-shielding layer has a light-shieldingportion that extends or is separated from the connecting line portion.The peripheral circuit can thereby be protected from light bydouble-layered light-shielding layers.

Sixteenthly, the present invention can provide a liquid crystal panelwhich suppresses a reduction in contrast due to the light leakagecurrent, and which comprises: a liquid crystal panel substrate accordingto the above-mentioned present invention; a light-incident-sidesubstrate positioned opposing the liquid crystal panel substrate with aspace therebetween; and a liquid crystal filled in the space.

Seventeenthly, the present invention can provide electronic equipmentwhich is equipped with the above liquid crystal panel as a displayportion, and which have a reflective type display device havingexcellent contrast at low electric power consumption.

Eighteenthly, the present invention can provide a small-sized projectiontype display device which has excellent contrast, and which comprises: alight source; the above liquid crystal panel reflecting and modulatingthe light emerging from the light source; and a projection optical meansfor collecting and projecting the light modulated by the liquid crystalpanel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a cross-sectional diagram showing an embodiment of a pixelregion on a reflective-electrode-side substrate of a reflective-typeliquid crystal panel to which the present invention is applied. FIG.1(b) is a cross-sectional diagram showing a border between a pixelregion and a peripheral region in the reflective-electrode-sidesubstrate of the reflective-type liquid crystal panel incorporated inthe present invention.

FIG. 2 is a cross-sectional diagram showing a peripheral region in areflective-electrode-side substrate of a reflective-type liquid crystalpanel incorporated in the present invention.

FIG. 3 is a plan layout diagram showing the embodiment of a pixel regionin the reflective-electrode-side substrate of the reflective-type liquidcrystal panel incorporated in the present invention.

FIGS. 4(a), 4(b) and 4(c) are cross-sectional diagrams showing otherembodiments of a structure of a space between pixel electrodes in areflective-electrode-side substrate of a reflective-type liquid crystalpanel incorporated in the present invention.

FIG. 5 is a plan diagram showing a structural example of a circuitlayout of a reflective-electrode-side substrate of a reflective-typeliquid crystal panel of the embodiment.

FIG. 6 is a cross-sectional diagram showing a structural example of areflective-type liquid crystal panel to which the liquid crystal panelsubstrate of the embodiment is applied.

FIG. 7 shows wave-forms of the voltages applied to the gate line and thedata line of a switching element of a pixel in a reflective-type liquidcrystal panel incorporated in the present invention.

FIG. 8 is a diagram showing a projection type display device to whichthe reflective-type liquid crystal panel of the embodiment is applied asa light valve.

FIGS. 9(a), 9(b) and 9(c) each show electronic equipment using thereflective-type liquid crystal panel of the present invention.

FIG. 10 is a cross-sectional diagram showing another embodiment of areflective-electrode-side substrate incorporated in the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained withreference to accompanying drawings.

(Description of a Liquid Crystal Panel Substrate Using a SemiconductorSubstrate)

FIGS. 1(a), 1(b) show the first embodiment of areflective-electrode-side substrate of a reflective-type liquid crystalpanel incorporated in the present invention. Among pixels arranged in amatrix pattern, one pixel is shown by the cross-sectional diagram andthe plan layout in FIGS. 1(a), 1(b), respectively. FIG. 1(a) is across-sectional diagram taken along the line I-I in FIG. 3. Similarly,FIG. 1(b) is a cross-sectional diagram taken along the line II-II inFIG. 3.

In FIGS. 1(a), 1(b), reference numeral 1 indicates a P-typesemiconductor substrate (may be an N-type semiconductor substrate (N⁻))such as single-crystal silicon, numeral 2 indicates a P-type well regionformed on the surface of the semiconductor substrate 1, and referencenumeral 3 indicates a field oxide film (so-called LOCOS) for separatingelements, which is formed on the front surface of the semiconductorsubstrate 1. Although the well region 2 is not particularly limited, itis formed as a common well region of a pixel region formed by arrangingpixels in a matrix pattern, such as 768×1024. Furthermore, the wellregion 2 may be formed separately from the well regions in whichtransistor elements comprising peripheral circuits are formed, such as adata-line driving circuit 21, a gate-line driving circuit 22, an inputcircuit 23, and a timing control circuit 24, as is shown in FIG. 5illustrating a plan diagram of the whole liquid crystal panel substrate.

The carriers generated in a well region, in which the peripheral circuitelements operated by high-frequency clock are formed, flow into anotherwell region of the pixel region, thereby causing the pixel transistorsto malfunction. The malfunction can be prevented by separating thewells. In addition, the following effect of electrostatic noise fromoutside can also be prevented by separating the wells: noise enters thewell region from the input circuit 23, reaches the portion of the wellin the pixel region, and causes pixel transistors to malfunction.

The field oxide film 3, with a thickness of approximately 5000 to 7000angstroms is formed by selective heat oxidation. In the field oxide film3, each pixel has two openings such that a gate electrode 4 a, made ofpoly-silicon, metallic silicide, etc. is formed in the center of oneopening with a gate oxide film (insulating film) 4 b interposedtherebetween, and source and drain regions 5 a and 5 b both formed of alayer doped with a high concentration of N-type impurity (hereinafterreferred to as doping layer) are formed at both sides of the gateelectrode 4 a on the surface of the substrate to form a field effecttype transistor (MOSFET) as a switching element. The gate electrode 4 ais extended in the scanning line direction (pixel row direction) to forma gate line 4.

A P-type doping region 8 is formed on the surface of the substrate inthe other opening made in the field oxide film 3, and a gate electrode 9a, made of poly-silicon, metallic silicide, etc. is formed on thesurface of the P-type doping region 8 with a gate oxide film (insulatingfilm) 9 b interposed therebetween so as to form an insulating filmcapacitor between the electrode 9 a and the P-type doping region 8. Theelectrode 9 a can be formed by the same process as that of thepoly-silicon or metallic silicide layer to be used as the gate electrode4 a of the MOSFET, and the insulating film 9 b below the electrode 9 acan be formed by the same step as that of the insulating film to be usedas the gate insulating film 4 b.

The insulating films 4 b and 9 b, with thicknesses of approximately 400to 800 angstroms, are formed on the surface of the semiconductorsubstrate inside the openings by heat oxidation. The electrodes 4 a and9 a are formed such that an approximately 1000 to 3000 angstroms thicksilicide layer is formed from a refractory metal, such as Mo or W, on anapproximately 1000 to 2000 angstroms thick polysilicon layer. The sourceand drain regions 5 a and 5 b are formed in a self aligned manner asfollows: by ion implantation, N-type impurities are doped into thesurface of the substrate at both sides of the gate electrode 4 a usingthe gate electrode 4 a as a mask. A portion of the well region justbelow the gate electrode 4 a is used as a channel region 5 c of theMOSFET.

In addition, preferably, the P-type doping region 8 is formed by dopingusing exclusive ion implantation and heat treatment, and is formed byion implantation before forming the gate electrode. In other words,after forming the insulating films 4 b and 9 b, impurities having thesame polarity as that of the well are implanted such that the surface ofthe well has a higher impurity concentration than the well so as toachieve low resistance. The preferred impurity concentration of the wellregion 2 is not more than 1×10¹⁷/cm³, and more preferably, 1×10¹⁶ to5×10¹⁶/cm³. Although the preferred surface impurity concentration of thesource and drain regions 5 a and 5 b is 1×10²⁰ to 3×10²⁰/cm³ and thepreferred surface impurity concentration of the P-type doping region 8is 1×10¹⁸ to 5×10 ¹⁹/cm³, 1×10¹⁸ to 1×10¹⁹/cm³ is particularlypreferable from the perspective of reliability and pressure durabilityof the insulating film forming a holding capacitor.

A first interlayer insulating film 6 informed on the electrodes 4 a and9 a and the field oxide film 3; data lines 7 (see FIG. 3), sourceelectrodes 7 a extended from the data lines, and auxiliary connectinglines 10 are formed of a metallic layer essentially consisting ofaluminum and provided on the insulating film 6 such that each sourceelectrode 7 a is electrically connected to the source region 5 a via acontact hole 6 a made in the insulating film 6, one end of eachauxiliary connecting line 10 is electrically connected to the drainregion 5 b via a contact hole 6 b made in the insulating film 6, and theother end of each auxiliary connecting line 10 is electrically connectedto the electrode 9 a via a contact hole 6 c made in the insulating film6.

For example, the insulating film 6 is formed by depositing a thicknessof approximately 8000 to 10000 angstroms of BPSG film (a silicate glassfilm containing boron and phosphorus) on HTO film (a silicon oxide filmformed by high-temperature CVD) having a thickness of an approximately1000 angstroms. For example, the metallic layer forming the sourceelectrode 7 a (data line 7) and the auxiliary connecting line 10 has afour-layer structure of Ti/TiN/Al/TiN from the bottom layer. Thethickness of each layer is as follows: 100 to 600 angstroms for thelower Ti layer, approximately 1000 angstroms for the TiN layer, 4000 to10000 angstroms for the Al layer, and 300 to 600 angstroms for the upperTiN layer.

A second interlayer insulating film 11 is formed over the sourceelectrode 7 a, the auxiliary connecting line 10, and the interlayerinsulating film 6, and a light-shielding layer (light-shielding layer),formed of a second metallic layer 12 essentially comprising aluminum, isformed on the second interlayer insulating film 11. The second metalliclayer 12 forming the light-shielding layer is also used as a metalliclayer forming a connecting line between elements in the peripheralcircuits such as a driving circuit formed around the pixel region, as isdiscussed below.

Therefore, it is unnecessary to add an extra step for forming thelight-shielding layer 12, resulting in a simpler process. Thelight-shielding layer 12 covers the entire pixel region, except for anopening 12 a, made at a position corresponding to the auxiliaryconnecting line 10, so as to pass a columnar connecting plug 15electrically connecting the undermentioned pixel electrode to theMOSFET. In other words, in the plan view shown in FIG. 3, a rectangularframe indicated by the reference numeral 12 a indicates the opening, andthe outside of the opening 12 a is the light-shielding layer 12. Lightincident on the upper side of FIG. 1 (the liquid crystal layer side) canthereby be cut off almost completely. Thus, it is possible to preventthe light leakage current generated by the light incident on the channelof the MOSFET used for switching the pixel and well regions.

For example, the second interlayer insulating film 11 is formed asfollows: using TEOS (tetraethylorthosilicate) as a material, a siliconoxide film (hereinafter referred to as TEOS film) of a thickness ofapproximately 3000 to 6000 angstroms is deposited by plasma CVO; an SOGfilm (spin on glass film) is deposited thereon and trimmed by etch back;and a second TEOS film of a thickness of approximately 2000 to 5000angstroms is deposited thereon. The second metallic layer forming thelight-shielding layer may be the same as that of the first metalliclayer 7 (7 a), and for example, it can have the four-layer structure ofTi/TiN/Al/TiN from the bottom layer. The thickness of each layer is asfollows: 100 to 600 angstroms for the bottom Ti layer, approximately1000 angstroms for the TiN layer, 4000 to 10000 angstroms for the Allayer, and 300 to 600 angstroms for the top TiN layer.

According to this embodiment, a third interlayer insulating film 13 isformed on the light-shielding layer 12, and on the third interlayerinsulating film 13, a pixel electrode 14 is formed as a rectangularreflective electrode substantially corresponding to one pixel, as isshown in FIG. 3. A contact hole 16 penetrating the third interlayerinsulating film 13 and the second interlayer insulating film 12 isformed inside the opening 12 a made in the light-shielding layer 12, andthe columnar connecting plug 15, which is made of a refractory metalsuch as tungsten, and which electrically connects the auxiliaryconnecting line 10 to the pixel electrode 14, is placed in the contacthole 16. In addition, a passivation film 17 is formed on the entirepixel electrode 14.

For assembling a liquid crystal panel, an alignment film is furtherformed on the reflective-electrode-side substrate, and then, an opposingsubstrate is positioned facing the substrate with a predetermined spacetherebetween. An opposing electrode (common electrode) is formed on theinner side of the opposing substrate beforehand, and the alignment filmis formed thereon. The periphery of the pair of substrates is fixed by asealing member, and then, a liquid crystal is poured and encapsulatedinto the thus-formed space to form a liquid crystal panel.

Although it is not particularly limited, after depositing tungsten, etc.comprising the connecting plug 15 by CVD, the tungsten and the thirdinterlayer insulating film 13 are planarized by a CMP (chemical machinepolish) method, the pixel electrode 14 is prepared, for example, byforming an aluminum layer of a thickness of approximately 300 to 5000angstroms according to a low-temperature sputtering method, and formedinto a square-like shape whose sides are approximately 15 to 20 μm bypatterning. The connecting plug 15 may be formed by making a contacthole after planarizing the third interlayer insulating film 13 by theCMP method, and then, depositing tungsten inside the contact hole. Asthe passivation film 17, a silicon oxide film of a thickness ofapproximately 500 to 2000 angstroms is used for the pixel region, and anitrogen oxide film of a thickness of approximately 2000 to 10000angstroms is used for the peripheral circuit portion, sealing portion36, and a scribe portion of the substrate. The sealing portion is formedby a sealing member for fixing a pair of substrates to assemble a liquidcrystal panel, as is mentioned above. The scribe portion is a portionalong the scribe region (i.e., the end portion of the liquid crystalpanel substrate) for separating numerous reflective-side liquid crystalpanel substrates of the present invention, formed in a semiconductorwafer, into semiconductor chips along scribe lines by dicing.

In addition, by using a silicon oxide film as the passivation film 17covering the pixel region, it is possible to prevent the reflectancefrom changing a great amount due to a variation in the film thickness orin response to a wavelength of the light.

Meanwhile, a silicon nitride film, which is superior to the siliconoxide films as a protective film in the light of water resistance of thesubstrate, etc. is employed as the passivation film 17 covering theperipheral region of the substrate, particularly, outside the region inwhich the liquid crystal is encapsuled (outside the sealing member). Thereliability can further be increased by employing a mono-layer structurehaving a silicon nitride film or a double-layer structure having asilicon nitride film formed on a silicon oxide film. In other words,moisture, etc. readily enters the peripheral region of the substrateexposed to the atmosphere, particularly in the scribe portion. Thus, thereliability and durability can be improved by covering such a portionwith a protective film of silicon nitride.

Wavelength dependency of the reflectance of the pixel electrode can bereduced in a reflective-side liquid crystal panel by setting thethickness of the passivation film formed on the reflective electrode towithin a range of from 500 to 2000 angstroms. At the time of assemblingthe liquid crystal panel, an alignment film made of a polyimide isformed on the entire surface of the passivation film 17 and subjected torubbing.

FIG. 3 is a plan layout diagram illustrating the reflective-side liquidcrystal panel substrate shown in FIG. 1. As is shown in the figure, thedata line 7 and the gate line 4 are formed to cross each other in thisembodiment. Since the gate line 4 also serves as the gate electrode 4 a,the portion of the gate line 4 indicated by hatching H in FIG. 3 is usedas the gate electrode 4 a, and a channel region 5 c of the pixelswitching MOSFET is formed on the surface of the substrate below thegate electrode 4 a. Source and drain regions 5 a and 5 b are formed onthe surface of the substrate at both sides of the channel region 5 c(shown as the upper and lower sides in FIG. 3). The source electrode 7 aconnected to the data line is formed such that it extends from the dataline 7 provided along the vertical direction of FIG. 3 and is connectedto the source region 5 a of the MOSFET via a contact hole.

In addition, the P-type doping region 8 forming one terminal of theholding capacitor is formed in parallel to the gate line 4 (pixel rowdirection) and connected to a P-type doping region of the adjacentpixel. The P-type doping region 8 is connected to a power source line 70via a contact hole 71, and a predetermined voltage V_(ss), such as 0 V(ground voltage), is applied to the P-type doping region 8. Thepredetermined voltage V_(ss) may be the same as, or approximately equalto, the voltage of the common electrode provided on the opposingsubstrate, the same, or approximately equal to, the center voltage ofthe amplitude of image signals supplied to the data line, or theintermediate voltage between the common electrode voltage and the centervoltage of the amplitude of image signal voltage.

By commonly connecting each P-type doping region 8 to the voltage V_(ss)in the outside of the pixel region, the voltage of one electrode of theholding capacitor is stabilized and the holding voltage held by theholding capacitor during the non-selected period of the pixel(non-conducting period of the MOSFET) is stabilized. Thus, variation involtage applied to each pixel electrode during one frame period can bereduced. In addition, undesired voltage variation of the pixel electrodecan be prevented. Furthermore, since the P-type doping region 8 ispositioned near the MOSFET and the voltage of the P well issimultaneously fixed, the fundamental voltage of the MOSFET isstabilized. Thus, the variation in the threshold voltage due to the backgate effect can be prevented.

Although not shown in the figures, the power source line 70 is also usedfor supplying the predetermined voltage V_(ss), as the well voltage, tothe P-type well region of the peripheral circuits provided outside thepixel region. The power source line 70 is formed of a first metalliclayer which is the same as the data line 7. The pixel electrode 14 isformed in a rectangular shape, provided near an adjacent pixel electrode14 at a distance of, for example, 1 μm, so as to reduce as much aspossible the amount of light leaking through the spaces between thepixel electrodes.

In the figures, the center of the shape of the pixel electrode isshifted from that of the contact hole 16. However, it is preferred thatthese centers are substantially coincident with, or superimposed onto,each other to reduce the amount of light leakage, since the traveldistance of the light, incident on the space between pixel electrodes,from the end portion of the pixel electrode to the contact hole, therebybecomes substantially the same for each end portion. This is because,since the second metallic layer 12 having light-shielding light isopened by the opening 12 a in the periphery of the contact hole 16, ifthe opening 12 a is provided near the end portion of the pixel electrode14, light which is incident from the space between the pixel electrodesis irregularly reflected between the second metallic layer 12 and theback surface of the pixel electrode 14, reaches the opening 12 a, and isincident to the lower substrate side from the opening, resulting inlight leakage. Therefore, by substantially matching or superimposing thecenter of the pixel electrode with that of the contact hole 16, thetravel distance of the light, incident on the space between the pixelelectrodes, from the end portion of the pixel electrode to the contacthole, thereby becomes substantially the same for each end portion of thepixel electrode. Thus, preferably, the light cannot readily reach thecontact hole, through which the light may enter the substrate side.

In the above embodiment, a case in which the pixel switching MOSFET isan N-channel type, and the semiconductor region 8 to be used as oneelectrode of the holding capacitor is a P-type doping layer isdescribed. However, it is also possible to have an N-type as the wellregion 2, a P-channel type as the pixel switching MOSFET and an N-typedoping layer as the semiconductor region to be used as one electrode ofthe holding capacitor. In such a case, similarly to the N-type wellregion, it is preferred that a predetermined voltage V_(DD) is appliedto the N-type doping layer to be used as one electrode of the holdingcapacitor. The predetermined constant voltage V_(DD) is preferably thevoltage of the higher side of the power source voltage, since it isapplied to the N-type well region. In other words, when the image signalvoltage applied to the source/drain of the pixel switching MOSFET is 5V, the predetermined constant voltage V_(DD) is preferably set to 5 V.

In addition, since a logic circuit and the like such as a shift registerof the peripheral circuits are driven by a small voltage such as 5 V(some of the peripheral circuits such as a circuit supplying scanningsignals to the gate lines are driven at 15 V), while a large voltagesuch as 15 V is applied to the gate electrode 4 a of the pixel switchingMOSFET, the following technology is considered: the gate insulating filmof a FET forming a peripheral circuit driven at 5 V is formed to bethinner than the gate insulating film of a pixel switching FET (byforming the gate insulating film by a separate step or by etching thesurface of the gate insulating film of the FET of a peripheral circuit)so as to increase the operation speed of the peripheral circuit(particularly the shift register of the data-line-side driving circuit,for which high-speed scanning is required) by improving the responsecharacteristics of the FET of the peripheral circuit. By employing thistechnique, the thickness of the gate insulating film of the FET forminga peripheral circuit can be decreased to approximately one third to onefifth (e.g. 80 to 200 angstroms) of that of the gate insulating film ofthe pixel switching FET in light of the pressure durability of the gateinsulating film.

FIG. 7 shows the driving waveforms in the first embodiment. In thefigure, V_(G) indicates the scanning signal applied to the gateelectrode of the pixel switching MOSFET, period t_(1H) indicates theselected period (scanning period) during which the MOSFET of the pixelconducts, and the other period is the non-selected period during whichthe MOSFET of the pixel does not conduct. Furthermore, V_(d) indicatesthe maximum amplitude of the image signals applied to the data line,V_(c) indicates the center voltage of the image signals, and LC-COMindicates the common voltage applied to the opposing (common) electrodeformed on the opposing substrate facing the reflective-electrode-sidesubstrate.

The voltage applied between the electrodes of the holding capacitor isdetermined by the difference between the image signal voltage V_(d)applied to the data line shown in FIG. 8 and the predetermined voltageV_(ss) such as 0V applied to the P-type semiconductor region 8. However,the necessary voltage difference fundamentally required to be applied tothe holding capacitor is approximately 5V, which is the differencebetween the image signal voltage V_(d) and the center voltage V_(c) ofthe image signals (although the common voltage LC-COM applied to theopposing (common) electrode 33 provided on the opposing substrate 35 ofthe liquid crystal panel shown in FIG. 6 is shifted by ΔV from theV_(c), the actual voltage applied to the pixel electrode is shifted byΔV and becomes V_(d)-ΔV). Thus, in the first embodiment, it is possiblethat the doping region 8 forming one terminal of the holding capacitorhas a polarity opposite to that of the well (arranged to be N-type inthe case of a P-type well), and is connected to the voltage ofapproximately V, or LC-COM in the periphery of the pixel region so as tohave a different voltage from the well voltage (e.g., the P-type well isat V_(ss)). The insulating film 9 b, just below the poly-silicon ormetallic silicide layer forming one electrode 9 a of the holdingcapacitor, can thereby be formed simultaneously with the gate insulatingfilm of the FET forming the peripheral circuits, not with the gateinsulating film of the pixel switching FET. Thus, the thickness of theinsulating film of the holding capacitor can be reduced to one third toone fifth of that of the above embodiment, and as a result, thecapacitance can be increased by three to five times.

FIG. 1(b) shows a cross-sectional view (FIG. 3 II-II) of a periphery ofa pixel region of an embodiment of the present invention. This is astructure for connecting the doping region 8, extending along thescanning direction (pixel row direction) of the pixel region, to thepredetermined voltage (V_(ss)). Reference numeral 80 indicates a P-typecontact region formed by the same step as that of the source/drainregions of the MOSFET of the peripheral circuits, such that afterforming the gate electrode, impurities having the same polarity areion-implanted with respect to the doping region 8 prepared beforeforming the gate electrode. The contact region 80 is connected to theline 70 via a contact hole 71, and the constant voltage V_(ss) isapplied thereto. The contact region 80 is also light-shielded by alight-shielding layer 14′, which is formed thereabove and which isformed of a third metallic layer. In other words, the light-shieldinglayer 14′ is formed in the peripheral region surrounding the entirepixel region and the light-shielding layer 14′ is separated from thepixel electrodes 14 of the pixels that are outermost in the pixelregion. The light-shielding layer 14′ is the same layer as the pixelelectrodes 14. A first metallic layer 12′ extends from thelight-shielding layer 12 that is outermost in the pixel region so as tolight-shield the light incident on the space between the outermost pixelelectrode 14 and the light-shielding layer 14′ in the peripheral region.

FIG. 2 is a cross-sectional diagram of an embodiment of a CMOS circuitelement forming the peripheral circuits such as a driving circuit in theoutside of the pixel region. In FIG. 2, the reference numerals identifya substantially identical metallic layer, insulating film, andsemiconductor region formed by the identical steps as those of FIG. 1.

In FIG. 2, numerals 4 a and 4 a′ indicate gate electrodes of anN-channel MOSFET and a P-channel MOSFET, respectively, forming theperipheral circuits (CMOS circuits), reference numerals 5 a (5 b) and 5a′ (5 b′) indicate an N-type doping region and a P-type doping region,respectively, each used to be the source (drain) region of the above,and 5 c and 5 c′ indicate channel regions. The contact region 80supplying a constant voltage to the P-type doping region 8 forming oneelectrode of the holding capacitor of FIG. 1 is formed by the same stepas that of the P-type doping region 5 a′ (5 b′) to be used as the source(drain) region of the P-channel MOSFET. Reference numerals 27 a and 27 cindicate source electrodes which are formed of a first metallic layerand connected to a power source voltage (0 V, 5 V, or 15 V), andreference numeral 27 b indicates a drain electrode formed of the firstmetallic layer. Reference numeral 32 a is a wiring layer formed of asecond metallic layer and is used as a line which connects elementsforming the peripheral circuits therebetween. Reference numeral 32 b isa power source line layer formed of the second metallic layer and isalso serves as a light-shielding layer. The light-shielding layer 32 bmay be connected to any constant voltage such as V_(c), LC-COM, or powersource voltage of 0 V, or it may be connected to inconstant voltagewhile being electrically separated from the power source line and thelike. Reference numeral 14′ is a third metallic layer, and in theperipheral circuit portion, the third metallic layer is used as alight-shielding layer to prevent light from being transmitted through asemiconductor region forming the peripheral circuits and from generatingcarriers which cause unstable voltage in the semiconductor region. Inother words, also in the peripheral circuits, light is light-shielded bythe second and third metallic layers.

As is mentioned above, the passivation film 17 in the peripheral circuitportion may be a silicon nitride film, which is superior as a protectivefilm to the silicon oxide film forming the passivation film of the pixelregion, or may be a protective film having a double-layer structure inwhich a silicon nitride film is formed on a silicon oxide film.Furthermore, although not particularly limited, the source/drain regionsof the MOSFET forming the peripheral circuits of this embodiment may beformed by a self-aligning manner. Any of the source/drain regions of theMOSFET may have a LDD (lightly doped drain) structure or a DDD (doubledoped drain) structure. Off-set structure (in which the gate electrodeand the source/drain regions are positioned with a distancetherebetween) is preferably employed for the pixel switching FETconsidering the fact that the FET is driven by a large voltage and itmust prevent the light leakage current.

FIGS. 4(a), 4(b), and 4(c) each indicate another embodiment of a liquidcrystal panel reflective-electrode-side substrate incorporated in thepresent invention. In FIGS. 4(a) to 4(c), the reference numeralsidentify substantially identical layers and semiconductor regions formedby the identical steps as those of FIGS. 1 and 2.

In the embodiment shown in FIG. 4(a), an anti-reflection film 18 formedof a material such as titanium nitride, i.e., TiN, is provided on theback surface of the pixel electrodes 14 of the embodiment shown inFIG. 1. Such an anti-reflection film 18 further increases thelight-shielding effect as compared with that in the first embodiment ofFIG. 1. In other words, since the light-shielding layer 12 provided inthe first embodiment is formed of a metallic layer having a relativelyhigh reflectance, such as aluminum, the light obliquely incident on aspace between the pixel electrodes 14, as is shown by reference numeralA in FIG. 4(a), is reflected by the surface of the light-shielding layer12, is further reflected by the back surface of a pixel electrode 14,and then, by repeating such reflection. The light may finally leakthrough the opening 12 a, which is provided at the position of theconnecting plug 15, to the MOSFET side, reach the substrate, and resultin a light leakage current. However, when the anti-reflection film 18 isprovided, it can absorb the light incident on the space between thepixel electrodes 14, and thus the light leakage current can further beeffectively prevented. The preferred thickness of the anti-reflectionfilm 18 formed of titanium nitride (TiN) is 500 to 1000 angstroms. Theanti-reflection film 18 may not only be formed on the back surface ofthe pixel electrodes, but also on the surface of the light-shieldinglayer 12 or intermediately in the interlayer insulating layer.

The embodiment shown in FIG. 4(b) is constructed as follows: in theembodiment shown in FIG. 4(a) in which the anti-reflection film 18 isprovided on the back surface of the pixel electrodes 14, a V-shapegroove 19 at least having a slope is formed between the adjacent pixelelectrodes on the surface of the third interlayer insulating film 13exposed to the space between the pixel electrodes 14. The lightvertically incident on the space between the pixel electrodes 14, as isshown by reference numeral B, is thereby reflected obliquely, and isabsorbed into the anti-reflection film 18 formed on the back surface ofthe pixel electrodes. Thus, the light, reflected by the surface of theinsulating film exposed to the space between the pixel electrodes or bythe underlying light-shielding layer, can be prevented from emergingwhile changing the direction by 180°. When such reflected light emerges,the image quality may deteriorate in a liquid crystal panel of anormally white mode in which the liquid crystal panel is allowed todisplay white by reflecting incident light when no voltage is applied tothe pixel electrodes, because the light emerging after being reflectedby the space between the pixel electrodes is displayed similarly to thelight reflected by a pixel electrode without an applied voltage.However, such reflected light can be eliminated by forming the V-shapegroove 19 as is shown in FIG. 4(b), in the interlayer insulating film13, thereby improving the image quality.

The embodiment shown in FIG. 4(c) is constructed as follows: in theembodiment shown in FIG. 4(a) in which the anti-reflection film 18 isprovided on the back surface of the pixel electrodes 14, a V-shapedgroove 19 is formed along the border between the pixel electrodes on thesurface of the light-shielding layer 12 positioned below the spacebetween the pixel electrodes 14. Similar effects to those of theembodiment of FIG. 4(b) are thereby obtained.

Although the groove 19 in FIGS. 4(b) and 4(c) has a V-shapedcross-section, the cross-sectional shape of the groove 19 is not limitedto the V-shape, and as long as the inner face of the groove has a slope,the incident light is reflected by the slope and changes its directionshifted by 180° with respect to the incident direction so that thereflected light is absorbed into the anti-reflection film. The shape ofthe groove may be such that a slope is formed along the end portion ofone pixel electrode and a vertical face is provided along the endportion of the adjacent pixel electrode, or may be formed into asubstantial V-shape groove with a small flat portion at the bottom orinto a plurality of rows of such grooves.

In the above structures shown in FIGS. 4(a), 4(b) and 4(c), in additionto the interlayer insulating film 13 formed of the above-mentioned TEOSfilm (including the SOG film left by partial etching), a silicon nitridefilm may be formed thereunder between the reflective electrodes 14 andthe underlying metallic layer as the light-shielding layer 12. On thecontrary, a silicon nitride film may be formed above the TEOS film 13.By employing such a double-layer structure, to which the silicon nitridefilm is added, for the interlayer insulating film 13, water or the likecannot readily enter the resulting film, thereby improving moistureresistance. The interlayer insulating film having such a double-layerstructure may be formed not only on the pixel region, but also on thesecond metallic layers 32 a and 32 b in the peripheral region, and themoisture resistance is thereby improved in the peripheral region. Inaddition, since the refractive index of the silicon nitride film isbetween 1.9 to 2.2, which value is higher than that of the silicon oxidefilm, i.e., 1.4 to 1.6, used for the protective insulating film 17, theincident light is reflected by the interface between the protectiveinsulating film 17 and the silicon nitride film, due to the differencein the refractive index when light is incident on the protectiveinsulating film 17 from the liquid crystal side. The amount of the lightincident on the interlayer film is thereby reduced. Thus, it is possibleto prevent the phenomenon that carriers are generated by the lightpassing through the semiconductor region and destabilize the voltage inthe semiconductor region.

FIG. 5 is a plan layout showing a whole liquid crystal panel substrate(reflective-electrode-side substrate) incorporated in the aboveembodiment.

In this embodiment, a light-shielding layer 25 is provided so as toprevent light from being incident on the peripheral circuits which areprovided in the periphery of the substrate, as is shown in FIG. 5. Thelight-shielding layer is formed from the same layer as that of the pixelelectrodes 14. The peripheral circuits are provided around the pixelregion 20 in which the pixel electrodes are arranged according to amatrix pattern. The peripheral circuits include: a data line drivingcircuit 21 supplying image signals, corresponding to image data, to thedata lines 7; a gate line driving circuit 22 scanning the gate lines 4in order; an input circuit 23 receiving image data input from outsidevia a pad region 26; a timing control circuit 24 controlling suchcircuits; and the like. These circuits are formed of: MOSFETs, as activeelements or switching elements, formed by the same or different step forforming the pixel electrode switching MOSFET; and load elements such asresistors or capacitors.

In this embodiment, the light-shielding layer 25 is formed of a thirdmetallic layer formed by the same step as that of the pixel electrodes14 shown in FIG. 1, and a predetermined voltage such as the power sourcevoltage, the center voltage of the image signals, or the LC commonvoltage is applied to the light-shielding layer 25. By applying thepredetermined voltage to the light-shielding layer 25, the reflectioncan be reduced as compared with applying a floating or other voltage.The light-shielding layer 25 can be allowed to float without connectingto a power source line. Displaying errors can thereby be avoided in theperipheral region, since the light-shielding layer 25 does not apply avoltage to the liquid crystal layer.

Reference numeral 26 indicates the pad region in which a pad or terminalused for supplying the power source voltage is formed. The sealingmember 36 is arranged such that the pad region 26 to which signals areinput from outside is positioned outside the sealing member 36.

FIG. 6 shows the cross-sectional structure of a reflective-type liquidcrystal panel to which the liquid crystal panel substrate 31 is applied.As is shown in FIG. 6, a support substrate 32 made of glass, ceramic,etc. is adhered to the back surface of the liquid crystal panelsubstrate 31 using an adhesive. Furthermore, an incident-side glasssubstrate 35, which is provided with an opposing electrode (also calledas common electrode) 33 made of a transparent conductive film (ITO), andto which the LC common voltage is applied, is positioned at the surfaceside of the liquid crystal panel substrate 31 with an appropriatedistance therebetween, and a known TN (Twisted Nematic) type liquidcrystal or a SH (Super Homeotropic) type liquid crystal 37, in whichliquid crystal molecules are aligned substantially homeotropicallywithout an applied voltage, is poured into the resulting space sealed bythe sealing member 36 to complete the liquid crystal panel 30.

The light-shielding layer 25 on the peripheral circuits is arranged toface the opposing electrode 33 with the liquid crystal 37 interposedtherebetween. Since the LC common voltage is applied to the opposingelectrode 33, by applying the LC common voltage to the light-shieldinglayer 25, no do voltage is applied to the liquid crystal interposedtherebetween. Therefore, the liquid crystal molecules are always twistedby approximately 90° in the case of the TN-type liquid crystal, and arealways aligned homeotropically in the case of the SH-type liquidcrystal.

In this embodiment, the strength of the liquid crystal panel substrate31 formed of a semiconductor substrate is significantly increasedbecause the liquid crystal panel substrate 31 has the support substrate32 made of glass, ceramic, etc. adhered to the back surface thereofusing the adhesive. As a result, by joining the opposing substrate tothe liquid crystal panel substrate 31 after adhering the supportsubstrate 32 to the liquid crystal panel substrate 31, a uniform gap isadvantageously obtained in the liquid crystal layer of the entire panel.

(Explanation of Liquid Crystal Panel Substrate Using InsulatingSubstrate)

Although the structure of a liquid crystal panel substrate using asemiconductor substrate and a liquid crystal panel employing the liquidcrystal panel substrate is explained above, the structure of areflective-type liquid crystal panel substrate using an insulatingsubstrate such as glass will be described below.

FIG. 10 shows a cross-sectional view of the structure of a pixel in areflective-type liquid crystal panel substrate. Similarly to FIG. 1,this figure shows a cross-sectional view taken along line I-I of theplan layout shown in FIG. 3. In this embodiment, a TFT is employed as atransistor for switching the pixel. In FIG. 10, the reference numeralsidentify layers and semiconductor regions having substantially identicalfunctions as those of FIGS. 1 and 2. Reference numeral 1 indicates asilica or non-alkaline glass substrate having a single-crystal,polycrystalline, or amorphous silicon film (the layer forming 5 a, 5 b,5 c, and 8) formed thereon, and insulating films 4 b and 9 b, having adouble-layer structure formed of a silicon oxide film formed by heatoxidation and another silicon oxide film or silicon nitride filmdeposited by CVD, are formed on the silicon film. Before forming theupper silicon oxide film or silicon nitride film of the insulating film4 b, N-type impurities are doped into the regions 5 a, 5 b, and 8 of thesilicon film to form the source region 5 a and drain region 5 b of aTFT, and the electrode region 8 of the holding capacitor. Furthermore, awiring layer which is made of poly-silicon, metallic silicide, etc., andwhich is to be used as the gate electrode 4 a of the TFT and the otherelectrode 9 a of the holding capacitor, is formed on the insulating film4 b. As is mentioned above, the TFT formed of the gate electrode 4 a,the gate insulating film 4 b, the channel 5 c, the source 5 a, and thedrain 5 b, and the holding capacitor formed of the electrodes 8 and 9 aand the insulating film 9 b are formed.

In addition, the first interlayer insulating film 6 made of siliconnitride or silicon oxide is formed on the wiring layers 4 a and 9 a, andthe source electrode 7 a connected to the source region 5 a via acontact hole made in the insulating film 6, is formed by a firstmetallic layer formed of an aluminum layer. The interlayer insulatingfilm 11 and the light-shielding layer 12 are formed on the firstmetallic layer similarly to those shown in FIG. 1. The second interlayerinsulating film 13 formed of silicon oxide, silicon nitride, or adouble-layer of silicon oxide and silicon nitride is formed on thelight-shielding layer 12. The second interlayer insulating film 13 isplanarized by the CMP method, and pixel electrodes, to be used asreflective electrodes, are formed from aluminum for each pixel on theplanarized second interlayer insulating film 13. The electrode region 8of the silicon film and the pixel electrode 14 are electricallyconnected via the contact hole 16. Similarly to that shown in FIG. 1,this connection is achieved by embedding the connecting plug 15 made ofa refractory metal such as tungsten. The light-shielding layer 12 isformed on the portion corresponding to the cross-sectional diagram ofFIG. 1(b), and a light-shielding layer 12′, which light-shields thelight incident on a space between the pixel electrode 14 and thelight-shielding layer 14′ light-shielding the peripheral region of thepixel electrode 14, is formed as a second metallic layer below the pixelelectrode 14 and the light-shielding layer 14′.

As is mentioned above, since the reflective electrode is positionedabove the TFT and holding capacitor formed on the insulating substrate,the pixel electrode region increases, and the holding capacitor also canbe formed in a larger area under the reflective electrode similarly tothe plan layout of FIG. 3. Thus, even in a high resolution (small pixel)panel, the drive is stabilized because the voltage applied to each pixelcan be maintained, and in addition, a high aperture ratio (reflectance)can be achieved.

As is similar to the above embodiments, the passivation film 17 formedof a silicon oxide film is formed on the reflective electrode 14. Thestructure of the liquid crystal panel substrate as a whole and that ofthe liquid crystal panel are similar to those shown in FIGS. 5 and 6.Therefore, the peripheral circuits such as the driving circuit employthe TFT as a transistor element. In the peripheral region including theperipheral circuit portion, the second metallic layers 32 a and 32 b areformed above the CMOS type TFT as connecting lines between the elementsand as a light-shielding layer elongated or separated therefrom, as issimilar to FIG. 2.

If light also enters from below the substrate, another light-shieldinglayer may be provided under the silicon films 5 a, 5 b, and 8. Althoughthe top-gate type in which the gate electrode is positioned above thechannel is shown in the figure, it is also good to provide thebottom-gate type in which the gate electrode is formed beforehand, and asilicon film to be used as the channel on a gate insulating filminterposed therebetween may be employed. Furthermore, moistureresistance of the peripheral circuit region can be improved by employingthe silicon nitride film or the double-layer structure film formed of asilicon oxide film and a silicon nitride film.

(Explanation of Electronic Equipment Using the Reflective-Type LiquidCrystal Panel of the Present Invention)

FIG. 8 shows electronic equipment using a liquid crystal panel of thepresent invention, and is a plan diagram illustrating the main portionof a projector (projection type display device) using reflective-typeliquid crystal panels of the present invention as light valves. FIG. 8shows a polarizing illuminator 100 having a light source portion 110positioned on the center line of an optical element 130, an integratorlens 120, and the polarization conversion element 130; a polarizationbeam splitter 200 reflecting the S-polarized light beam, emerging fromthe polarizing illuminator 100, by a S-polarized light reflectionsurface 201; a dichroic mirror 412 separating a blue light (B) componentfrom the light reflected by the S-polarized light reflection surface 201of the polarization beam splitter 200; a reflective-type liquid crystallight valve 300B modulating the separated blue light (B); a dichroicmirror 413 reflecting the light, from which the blue light has beenseparated, and separating a red light (R) component therefrom; areflective-type liquid crystal light valve 300R modulating the separatedred light (R); a reflective-type liquid crystal light valve 300Gmodulating the residual green light (G) transmitted through the dichroicmirror 413; and a projection optical system 500 formed of projectionlenses by which light, that is modulated by the three reflective-typeliquid crystal light valves 300R, 300G, and 300B and then synthesized bythe dichroic mirrors 412 and 413 and the polarization beam splitter 200,is projected on a screen 600. Each of the three reflective-type liquidcrystal light valves 300R, 300G, and 300B is provided with the liquidcrystal panel.

The randomly polarized light beam emerging from the light source portion110 is separated into a plurality of intermediate light beams by theintegrator lens 120, converted into one type of polarized light beams(S-polarized light beams) polarized in substantially the same directionby the polarization conversion element 130 having a second integratorlens on the light-incident side, and reaches the polarization beamsplitter 200. The S-polarized light beams emerging from the polarizationconversion element 130 are reflected by the S-polarized light reflectionsurface 201 of the polarization beam splitter 200, and among thereflected light beams, the blue light (B) beams are reflected by theblue light reflection layer of the dichroic mirror 412 and are modulatedby the reflective-type liquid crystal light valve 300B. Among the lightbeams transmitted through the blue light reflection layer of thedichroic mirror 412, the red light (R) beams are reflected by the redlight reflection layer of the dichroic mirror 413 and are modulated bythe reflective-type liquid crystal light valve 300R.

Meanwhile, the green light (G) beams transmitted through the red lightreflection layer of the dichroic mirror 413 are modulated by thereflective-type liquid crystal light valve 300G. The reflective-typeliquid crystal panel in which modulation is carried out by thereflective-type liquid crystal light valves 300R, 300G, and 300Baccording to the above-mentioned manner employs the TN-type liquidcrystal (in which the major axis of liquid crystal molecules is alignedsubstantially parallel to the panel substrate under no applied voltage)or the SH-type liquid crystal (in which the major axis of liquid crystalmolecules is aligned substantially perpendicular to the panel substrateunder no applied voltage).

When employing the TN-type liquid crystal, in a pixel (OFF pixel) inwhich a voltage below the threshold voltage of the liquid crystal isapplied to the liquid crystal layer interposed between the reflectiveelectrode of the pixel and the common electrode of the opposingsubstrate, the incident color light is elliptically polarized by theliquid crystal layer, is reflected by the reflective electrode, andemerges via the liquid crystal layer as the nearly ellipticallypolarized light beams whose polarization axis component is almostentirely shifted by substantially 90° from the polarization axis of theincident color light. Meanwhile, in a pixel (ON pixel) in which avoltage is applied to the liquid crystal layer, the incident color lightreaches the reflective electrode unchanged, is reflected, and emergeswhile maintaining the same polarization axis as that of the incidentlight. Since the alignment angle of the liquid crystal molecules of theTN-type liquid crystal changes according to the voltage applied to thereflective electrode, the angle of the polarization axis of thereflected light with respect to the incident light varies with thevoltage applied to the reflective electrode via the transistor of thepixel.

In addition, when employing the SH-type liquid crystal, in a pixel (OFFpixel) in which the voltage applied to the liquid crystal layer is belowthe threshold voltage of the liquid crystal, the incident color lightreaches the reflective electrode unchanged, is reflected, and emergeswhile maintaining the same polarization axis as that of the incidentlight. Meanwhile, in a pixel (ON pixel) in which a voltage is applied tothe liquid crystal layer, the incident color light is ellipticallypolarized by the liquid crystal layer, is reflected by the reflectiveelectrode, and emerges via the liquid crystal layer as the nearlyelliptically polarized light beams whose polarization axis component isalmost entirely shifted by substantially 90° from the polarization axisof the incident light. Similarly to the TN-type liquid crystal, thealignment angle of the liquid crystal molecules of the SH-type liquidcrystal changes according to the voltage applied to the reflectiveelectrode, and the angle of the polarization axis of the reflected lightwith respect to the incident light varies with the voltage applied tothe reflective electrode via the transistor of the pixel.

Among the color light reflected by the pixels of the liquid crystalpanel, the polarization beam splitter 200, which reflects S-polarizedlight, passes the P-polarized component, but does not pass theS-polarized component. The light transmitted through the polarizationbeam splitter 200 forms an image. Therefore, when the TN-type liquidcrystal is employed for the liquid crystal panel, the projected image isin the normally white mode, since the reflected light of the OFF pixelreaches the projection optical system 500 and that of the ON pixel doesnot reach the lens. When the SH-type liquid crystal is employed, theprojected image is in the normally black mode, since the reflected lightof the OFF pixel does not reach the projection optical system and thatof the ON pixel reaches the projection optical system 500.

According to the reflective-type liquid crystal panel, by utilizing asemiconductor technique, a larger number of pixels can be formed and thepanel size can be reduced as compared with active-matrix liquid crystalpanel having a TFT array formed on a glass substrate. Thus, images withhigher resolution can be projected by smaller-sized projectors.

As is described with reference to FIG. 6, the peripheral circuit portionof the liquid crystal panel is covered with a light-shielding layer andthe same voltage (e.g., LC common voltage, however, if the LC commonvoltage is not applied, a voltage different from the opposing electrodeof the pixel portion is applied, thus a peripheral opposing electrode isseparated from the opposing electrode of the pixel portion) as thatapplied to the opposing electrode formed on the opposing substrate isapplied to the peripheral circuit portion. Thus, substantially 0 V isapplied to the liquid crystal interposed therebetween and the liquidcrystal is in the OFF state. Therefore, in accordance with the normallywhite mode, the entire periphery of the image region can display whitemode in a TN-type liquid crystal panel, and the entire periphery of theimage region can display black mode in a SH-type liquid crystal panel inaccordance with the normally black mode.

According to the above embodiment, the voltage applied to each of thereflective-type liquid crystal panels 300R, 300G, and 300B issufficiently maintained and also the reflectance of each pixel electrodeis extremely high. Thus, sharp images can be obtained.

FIGS. 9(a), 9(b) and 9(c) show an outside view of electronic equipmentemploying a reflective-type liquid crystal panel of the presentinvention. The reflective-type liquid crystal panels employed in theseelectronic equipment fundamentally have the same structure as those usedas the light valves, except that the reflective electrodes are notrequired to have a completely reflective face, and far from it, thereflective electrodes preferably have an appropriately roughened surfaceto increase the angle of view because the reflective-type liquid crystalpanels are used as direct viewing reflective-type liquid crystal panelsin these electronic equipment and are not used as light valves combinedwith a polarization beam splitter.

FIG. 9(a) is a perspective view showing a cellular telephone. Referencenumeral 1000 indicates the main body of the cellular telephone andreference numeral 1001 indicates a liquid crystal display portion usinga reflective-type liquid crystal panel of the present invention.

FIG. 9(b) shows wrist-watch-type electronic equipment. Reference numeral1100 indicates the main body of the watch. Reference numeral 1101indicates a liquid crystal display portion using a reflective-typeliquid crystal panel of the present invention. Since the liquid crystalpanel has pixels of higher resolution as compared with conventionalwatch display portion, it can display TV images, achievingwristwatch-type TVs.

FIG. 9(c) shows a mobile data-processing device of a word processor or apersonal computer. Reference numeral 1200 indicates the data-processingdevice, reference numeral 1202 indicates an input unit such as akeyboard or the like, reference numeral 1206 indicates a display portionusing a reflective-type liquid crystal panel of the present invention,and reference numeral 1204 indicates the main body of thedata-processing device. Since each of the electronic equipment is drivenby batteries, the life-time of the batteries can be extended by using areflective-type liquid crystal panel that does not have a light sourcelamp. In addition, as is mentioned in the present invention, theperipheral circuits can be built in the panel substrate; the number ofcomponents is largely reduced, and more light-weight and smaller-sizedequipment can be achieved.

In the above embodiments, the TN-type liquid crystal, and the SH-typeliquid crystal which is homeotropically aligned, are employed as theliquid crystal for liquid crystal panels. However, the present inventioncan be realized by using other types of liquid crystals.

As is mentioned above, according to the present invention, alight-shielding layer is made between a pixel electrode, which is usedas a reflective electrode, and a conductive layer, which constitutes aterminal electrode of a switching element applying a voltage to thepixel electrode, such that in the pixel region, the light-shieldinglayer has only an opening for forming a contact hole connecting thepixel electrode and the terminal electrode. Thus, the amount of lightleaking from the incident side to the driving-element side can bereduced to substantially zero and the amount of a light leakage currentflowing in a semiconductor layer or semiconductor substrate can belargely decreased.

In addition, in a reflective-type liquid crystal panel having a pixelregion, in which the pixel electrodes are arranged in a matrix pattern,and peripheral circuits provided around the pixel region on the samesubstrate, a light-shielding layer formed of the same layer as ametallic layer forming the reflective electrodes in the pixel region isprovided for the peripheral circuits. Thus, without increasing thenumber of process steps, the amount of light leakage in the pixel regionand the peripheral circuits can be reduced, thereby decreasing the lightleakage current.

Moreover, in a reflective-type liquid crystal panel having a pixelregion, in which the pixel electrodes are arranged in a matrix pattern,and peripheral circuits provided around the pixel region on the samesubstrate, a light-shielding layer of the pixel region is formed belowthe pixel electrode layer from a layer used as a wiring layer or alight-shielding layer of the peripheral circuits. Thus, thelight-shielding layer can be formed without increasing the number ofprocess steps.

Furthermore, since an anti-reflection film is formed at the bottom sideof the pixel electrode, the light reflected by the surface of thelight-shielding layer can be absorbed, even if the light-shielding layeris formed of a metallic layer having a relatively high reflectance.Thus, the following phenomenon can be prevented: the light repeatedlyreflected between the surface of the light-shielding layer and the backsurface of the pixel electrode leaks through an opening provided at theportion of a conductor which connects a pixel electrode and a switchingelectrode, reaches the semiconductor layer or the semiconductorsubstrate, and generates a light leakage current.

In addition, an anti-reflection film is formed at the bottom side of thepixel electrode and a groove at least having a slope is formed betweenpixel electrodes on the surface of an insulating film exposed to a spacebetween the pixel electrodes in the pixel region or on the surface of alight-shielding layer below the insulating film. Thus, the lightincident on the space between the pixel electrodes is reflected in anoblique direction and is absorbed into the anti-reflection film on theback surface of the pixel electrodes so that the light reflected by thesurface of the insulating film, exposed to the space between the pixelelectrodes, or the light-shielding layer below the insulating film, isprevented from emerging while changing its direction by 180°. Therefore,the image quality can be improved.

1. A substrate having a pixel electrode, comprising: a substrate; aplurality of pixel units, each pixel unit including a pixel electrodeuseable as a reflective electrode and a switching element electricallyconnected to the pixel electrode, the pixel units being arranged in amatrix pattern on the substrate, the switching element having a terminalelectrode forming a conductive layer, a contact hole provided betweenthe pixel electrode and the conductive layer that electrically connectsthe pixel electrode and the terminal electrode; a light-shielding layerhaving an opening surrounding a portion in which the contact hole isformed and having no opening in regions between adjacent pixelelectrodes, the light-shielding layer being formed between the pixelelectrode and the conductive layer; and an underlying insulating layerbeing formed below the pixel electrodes, and in regions between adjacentpixel electrodes of the plurality of pixel units, a groove having noflat surface on bottom and having a substantially V-shaped surfacerelative to an upper surface of the underlying insulating layer beingformed in regions between adjacent pixel electrodes on a surface of thelight-shielding layer under the underlying insulating layer, theV-shaped surface for reflecting obliquely the light vertically incidentwhich enters a space between the pixel electrodes.
 2. The substratehaving a pixel electrode as set forth in claim 1, wherein ananti-reflection film is provide between the pixel electrode and thelight-shielding layer.
 3. The substrate having a pixel electrode as setforth in claim 2, wherein the anti-reflection film has substantially thesame planar shape as that of the pixel electrode and is provided belowthe pixel electrode.
 4. The substrate having a pixel electrode as setforth in claim 2, wherein the anti-reflection film comprises titaniumnitride.
 5. The substrate having a pixel electrode as set forth in claim4, wherein the film thickness of the titanium nitride is 500 to 1000angstroms.
 6. The substrate having a pixel electrode as set forth inclaim 1, the anti-reflection film having substantially the same shape asthat of the pixel electrode, and being provided below the pixelelectrode.
 7. The substrate having a pixel electrode as set forth inclaim 6, wherein the anti-reflection film comprises titanium nitride. 8.The substrate having a pixel electrode as set forth in claim 7, whereinthe film thickness of the titanium nitride is 500 to 1000 angstroms. 9.The substrate having a pixel electrode as set forth in claim 1, whereinthe contact hole is provided at a substantially central position of aplane of the pixel electrode.
 10. A substrate having a pixel electrode,comprising: a substrate; a plurality of pixel units, each pixel unitincluding a pixel electrode useable as a reflective electrode and aswitching element electrically connected to the pixel electrode, thepixel units being arranged in a matrix pattern on the substrate, theswitching element having a terminal electrode forming a conductivelayer, a connecting wiring provided between the pixel electrode and theconductive layer that electrically connects the pixel electrode and theterminal electrode; a light-shielding layer having an openingsurrounding a portion in which the connecting wiring is formed andhaving no opening in regions between adjacent pixel electrodes, thelight-shielding layer being formed between the pixel electrode and theconductive layer; and an underlying insulating layer being formed belowthe pixel electrodes, and in regions between adjacent pixel electrodesof the plurality of pixel units, a groove defined by a pair of slopingsurfaces relative to an upper surface of the underlying insulating layerbeing formed in regions between adjacent pixel electrodes on a surfaceof the light-shielding layer under the underlying insulating layer, thepair of sloping surfaces of the groove being opposed to each other andthe groove having no flat surface on bottom, the groove for reflectingobliquely the light vertically incident which enters a space between thepixel electrodes.
 11. A substrate having a pixel electrode, comprising:a substrate; a plurality of pixel units, each pixel unit including apixel electrode useable as a reflective electrode and a switchingelement electrically connected to the pixel electrode, the pixel unitsbeing arranged in a matrix pattern on the substrate, the switchingelement having a terminal electrode forming a conductive layer, aconnecting wiring provided between the pixel electrode and theconductive layer that electrically connects the pixel electrode and theterminal electrode; a light-shielding layer having an openingsurrounding a portion in which the connecting wiring is formed andhaving no opening in regions between adjacent pixel electrodes, thelight-shielding layer being formed between the pixel electrode and theconductive layer; and an underlying insulating layer being formed belowthe pixel electrodes, and in regions between adjacent pixel electrodesof the plurality of pixel units, a groove having no flat surface onbottom and having a substantially V-shaped surface relative to an uppersurface of the underlying insulating layer being formed in regionsbetween adjacent pixel electrodes on a surface of the light-shieldinglayer under the underlying insulating layer, the groove for reflectingobliquely the light vertically incident which enters a space between thepixel electrodes.